The invention generally relates to a rotary actuator mechanism for a downhole tool.
A downhole tool is a device that performs a specific function in a well, such as, for example, controlling a production flow in the well. A typical downhole tool may include a piston that moves linearly along the longitudinal axis of the tool. The piston typically has a cylindrical form and is oriented to travel in a direction that is parallel to the longitudinal axis of the tool.
More specifically, the piston typically translates linearly along the longitudinal axis of the tool when subjected to hydraulic control pressure. The piston may be used for such purposes as shifting a sliding sleeve to selectively open and close apertures to control the flow of fluid through a valve, for example.
In some cases, a rotational motion may be needed in the tool. For these cases, the linear motion of the piston may be converted to a rotational motion through a rotational conversion mechanism such as a “J-slot.” However, this approach may introduce a relatively inefficient energy conversion and its operation may be somewhat unreliable. Additionally, the use of a linear piston in combination with a rotational conversion mechanism has the inability to fail in a particular operational position, may be expensive, may be difficult to manufacture and may further add to the cost and complexity of the tool.
Thus, there exists a continuing need for better ways to produce rotational motion in a tool about its longitudinal axis.